Question Need some help with transistors... flickering signal both on and off

Oct 22, 2021
So I'm trying to connect a rpi Pico to a bluetooth game controller (8bitdo Zero 2), so that I can use the controller as an 'idle player' so to speak. I was planning on doing this by soldering transistors onto the button contacts so I could control them by the GPIO pins on the Pico.

However this resulted in a flickery, unpredictable signal. But only when the B pin was connected. (when it was connected it didn't matter if the GPIO was on or not, it still flickered).
I'm thinking that transistors aren't as simple as a 'digital switch' like I thought they were.

I'm using ksp2222a transistors, and I was connecting everything directly. No resistors -- If that's bad, I've tested everything afterwards and nothing broke, and I have extras of everything just in case. The buttons on the controller work by a common voltage line that, from what I observe, determines the button pressed by different resistances to ground.

Any advice or alternatives would be greatly appreciated.